1. Field of the Invention
The present invention relates to a gas detection method, a gas detection system, and a gas desorption method.
2. Description of the Related Art
A gas detection element that detects gas floating in the air adsorbs a specific kind of gas molecules included in the air, and detects target gas by detecting the presence or absence of the adsorption and an adsorption amount. As an example of the sensor, a sensor using a mass microbalance method is known.
In the sensing by the mass micro balance method, the dielectric sensor is vibrated at a constant frequency (resonant frequency) by applying a voltage to a fine dielectric sensor (piezoelectric sensor), and a mass increase due to the gas adsorption on the surface of the dielectric sensor is detected as a decrease in resonant frequency. As a typical example of this dielectric sensor, Quartz Crystal Mass micro balance (QCM) is known.
In the QCM, electrodes are provided on both sides of a thin film of quartz cut out at a specific angle (AT-cut), and a voltage is applied, to cause shear vibration at resonant frequency in the horizontal direction with the quartz plane. Since this resonant frequency decreases according to the mass of the gas adsorbed on the electrode, it is possible to recognize the mass change of the substance on the electrode.
Besides quartz, ceramic dielectric materials (piezoelectric materials) such as lead zirconate titanate (PZT), zinc oxide (ZnO), and aluminum nitride (AIN) can be applied to the mass micro balance method. Unlike the quartz, a film can be formed with these materials by a sputtering method, a vacuum evaporation method, and the like, and there is an advantage in that a small gas detection element can be manufactured by a Micro Electro Mechanical Systems (MEMS) technique.
For example, in JP1995-209163A (JP-H07-209163A), as the gas detection element using a mass micro balance method, a gas detection sensor including a specific vibrator plate provided with a pair of electrodes, a gas adsorption film made of metal oxide formed on at least one of the electrodes, or a heater for heating the gas adsorption film is disclosed. According to the technology disclosed in JP1995-209163A (JP-H07-209163A), the adsorption gas can be desorbed by the heating of the heater, and thus, it is considered that, even in a case where the number of times of the measurement is increased, the sensitivity is not likely to decrease.